Alternating Current PYQs Set 4 (PDF)

Set 4 of 9 · Questions 91-120 of 244

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Mere Teacher · Previous Year Questions NEET Physics · Alternating Current · Set 4 (Q91-120)
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91. $The coil of a.c. generator has 100 turns, each of cross. sectional area 2 m^{2} . It is rotating at constant angular speed 30 rad / s, in a uniform magnetic field of 2 \times 10^{- 2} T . If the total resistance of the circuit is 600Ω then maximum power dissipated in the circuit is$ (1) $6 W$ (2) $9 W$ (3) $12 W$ (4) $24 W$ 92. $A resistance of 40 Ω is connected to a source of alternating current rated 220 V, 50 Hz. Find the time taken by the current to change from its maximum value to rms value:$ (1) $2.5 ms$ (2) $1.25 ms$ (3) $2.5 s$ (4) $0.25 s$ 93. $A 40 μF capacitor is connected to a 200 V, 50 Hz AC supply. The rms value of the current in the circuit is, nearly [NEET 2020]$ (1) $2.05 A$ (2) $2.5 A$ (3) $25.1 A$ (4) $1.7 A$ 94. $An electric bulb rated as 100 W - 220 V is connected to an ac source of rms voltage 220 V. The peak value of current through the bulb is:$ (1) $0.32 A$ (2) $0.64 A$ (3) $0.45 A$ (4) $2.2 A$ 95. $The energy stored in a coil of inductance L carrying a steady current i is in the form$ (1) $magnetic$ (2) $electrical$ (3) $both magnetic and electrical$ (4) $heat$ 96. $An alternating voltage E = 2002 sin (100 t) volt is connected to a 1 μF capacitor through an a.c. ammeter. The reading of the ammeter shall be$ (1) $10 mA$ (2) $40 mA$ (3) $20 mA$ (4) $80 mA$ 97. $A capacitor C is first charged fully with potential difference of V_{0} and disconnected from the battery. The charged capacitor is connected across an inductor having inductance L . In t s 25 % of the initial energy in the capacitor is transferred to the inductor. The value of t is____s.$ (1) $\frac{π LC}{3}$ (2) $\frac{π LC}{6}$ (3) $\frac{π LC}{2}$ (4) $π \frac{LC}{2}$ 98. $In a series LCR circuit R = 300Ω, L = 0.9 H, C = 2 μF, ω = 1000 rad / s . The impedance of the circuit is$ (1) $500Ω$ (2) $1300Ω$ (3) $400Ω$ (4) $900Ω$ 99. $LC oscillations are similar and analogous to the mechanical oscillations of a block attached to a spring. The electrical equivalent of the force constant of the spring is$ (1) $reciprocal of capacitive reactance$ (2) $capacitive reactance$ (3) $reciprocal of capacitance$ (4) $capacitance.$ 100. $The reactance of an inductor at 50 Hz is 10Ω . The reactance of it at 200 Hz is$ (1) $10Ω$ (2) $40Ω$ (3) $2.5Ω$ (4) $20Ω$ 101. $A resistor of resistance R and an inductor of inductive reactance R are connected in series to an ac source. A capacitor of capacitive reactance 2 R is then connected in series with L and R . The ratio of the power fators of LR and LCR circuits is$ (1) $1 : 1$ (2) $1 : 2$ (3) $1 : 3$ (4) $2 : 3$ 102. $An ideal choke draws a current of 8 A when connected to an AC supply of 100 V, 50 Hz . A pure resistor draws a current of 10 A when connected to the same source. The ideal choke and the resistor are connected in series and then connected to the AC source of 150 V, 40 Hz . The current in the circuit becomes$ (1) $\frac{15}{2} A$ (2) $8 A$ (3) $18 A$ (4) $10 A$ 103. $For a series LCR circuit with R = 100Ω, L = 0.5 mH and C = 0.1pF connected across 220V-50Hz AC supply, the phase angle between current and supplied voltage and the nature of the circuit is:$ (1) $0^{0}, resistive circuit$ (2) $\approx 9 0^{0}, predominantly inductive circuit$ (3) $0^{0}, resonance circuit$ (4) $\approx 9 0^{0}, predominantly capacitive circuit$ 104. $When a capacitor is connected to a battery$ (1) $an alternating current flow in the circuit$ (2) $no current flow in the circuit$ (3) $a current flow for sometime and finally it decreases to zero$ (4) $current keeps on increasing and reaches maximum after sometime$ 105. $In R - L - C series circuit, the potential differences across each element is 20 V . Now the value of the resistance alone is doubled, then P.D. across R, L and C respectively$ (1) $20 V, 10 V, 10 V$ (2) $20 V, 20 V, 20 V$ (3) $20 V, 40 V, 40 V$ (4) $10 V, 20 V, 20 V$ 106. $In an LCR circuit, at resonance$ (1) $the impedance is maximum$ (2) $the current leads the voltage by π /2$ (3) $the current and voltage are in phase$ (4) $the current is minimum.$ 107. $A copper wire of radius 0.1 mm and resistance 2 kΩ is connected across a power supply of 40 V . The number of electrons transferred per second between the supply and the wire at one end is$ (1) $2.00 \times 10^{16}$ (2) $1.25 \times 10^{17}$ (3) $2.85 \times 10^{17}$ (4) $3.25 \times 10^{16}$ 108. $A circuit when connected to an AC source of 12 V gives a current of 0.2 A. The same circuit when connected to a DC source of 12 V, gives a current of 0.4 A. The circuit is [NEET 2019]$ (1) $series LR$ (2) $series RC$ (3) $series LC$ (4) $series LCR$ 109. $In an LCR series circuit, if the angular frequency is gradually increased then match the following columns Column-I (A) Capacitive reactance (B) Inductive reactance (C) Resistance (D) Total impedance Column-II (I) will continuously increase (II) will remain constant (III) will first decrease and then increase (IV) will continuously decrease$ (1) $(A)-(I), (B)-(III), (c)-(IV), (D)-(II)$ (2) $(A)-(IV), (B)-(I), (c)-(II), (D)-(III)$ (3) $(A)-(I), (B)-(IV), (c)-(II), (D)-(III)$ (4) $(A)-(II), (B)-(III), (c)-(I), (D)-(IV)$ 110. $An alternating voltage is applied to a series LCR circuit. If the current leads the voltage by 45^{\circ}, then (tan 45^{\circ} = 1)$ (1) $X_{L} = X_{C} - R$ (2) $X_{L} = X_{C} + R$ (3) $X_{C} = X_{L}^{2} + R^{2}$ (4) $X_{L} = X_{C}^{2} + R^{2}$ 111. $In a circuit L, C and R are connected in series with an alternating voltage source of frequency f . When current in the circuit leads the voltage by 45^{\circ}, the value of C is$ (1) $\frac{1}{2 πf ( 2 πfL + R )}$ (2) $\frac{1}{2 πf ( 2 πfR + L )}$ (3) $\frac{2}{2 πf ( R + L )}$ (4) $\frac{2}{2 πf ( R + \frac{1}{L} )}$ 112. $An alternating current is given by i = (2 sin ωt + 6 cos ωt) A . The rms current (in A) is$ (1) $25$ (2) $210$ (3) $5$ (4) $102$ 113. $Capacitive reactance of a capacitor in an AC circuit is 6 kΩ . If the same capacitor is connected to an AC source of double the frequency, the capacitive reactance will become$ (1) $6 kΩ$ (2) $3 kΩ$ (3) $1.5 kΩ$ (4) $8.5 kΩ$ 114. $An alternating voltage is given by E = 100 sin (ωt + π /6) V . The voltage will be maximum for the first time when t = [T = periodic time]$ (1) $T /12$ (2) $T /2$ (3) $T /6$ (4) $T /3$ 115. $When a coil is connected to AC supply of frequency 50 Hz, a current of 4 A flows in it and it consumes 240 W power. If the potential difference across the coil is 100 V, then the inductance value of the coil is$ (1) $L = (5 π) H$ (2) $L = \frac{π}{5} H$ (3) $L = \frac{1}{5 π} H$ (4) $L = \frac{1}{25 π} H$ 116. $An alternating voltage V (t) = 220 sin 100 πt volt is applied to a purely resistive load of 50Ω . The time taken for the current to rise from half of the peak value to the peak value is:$ (1) $5 ms$ (2) $3.3 ms$ (3) $7.2 ms$ (4) $2.2 ms$ 117. $ALCR circuit is at resonance for a capacitor C, inductance L and resistance R . Now the value of resistance is halved keeping all other parameters same. The current amplitude at resonance will be now:$ (1) $Zero$ (2) $same$ (3) $halved$ (4) $double$ 118. $An electric bulb has a rated power of 50 W at 100 V . If it is used on an a.c. source 200 V, 50 Hz, a choke has to be used in series with it. This choke should have an inductance of$ (1) $0.1 mH$ (2) $1 mH$ (3) $0.1 H$ (4) $1.1 H$ 119. $Match List-I with List-II: List-I (A) ωL > \frac{1}{ωC} (B) ωL = \frac{1}{ωC} (C) ωL < \frac{1}{ωC} (D) Resonant frequency List-II (I) Current is in phase with emf (II) Current lags behind the applied emf (III) Maximum current occurs (IV) Current leads the emf Choose the correct answer from the options given below$ (1) $(A) -(II); (B) - (I); (C) - (IV); (D) - (III)$ (2) $(A) -(II); (B) - (I); (C) - (III); (D) - (IV)$ (3) $(A) -(III); (B) - (I); (C) - (IV); (D) - (II)$ (4) $(A) -(IV); (B) - (III); (C) - (II); (D) - (I)$ 120. $An LCR circuit contains resistance of 110 Ω and a supply of 220 V at 300 rad / s angular frequency. If onlycapacitance is removed from the circuit, current lags behind the voltage by 45^{\circ} . If on the other hand, only inductor is removed the current leads by 45^{\circ} with the applied voltage. The rms current flowing in the circuitwill be:$ (1) $2.5 A$ (2) $2 A$ (3) $1 A$ (4) $1.5 A$